Devices of this type are used, for example, but by no means exclusively, for the manual actuation of the gears or for gear preselection in gear change mechanisms of motor vehicles.
Actuating device of the type mentioned in the introduction are used in motor vehicles to actuate a great variety of systems and functions of the motor vehicle. Numerous systems and functions are operated electrically or controlled electronically in modern motor vehicles. This applies both to complex mechanical assembly units of the powertrain, for example, manually or automatically controlled vehicle transmissions, and simpler functions, such as electric seat adjustment, windshield wiper drives, to diverse electronic systems in the vehicle and the like. However, gear preselection and control of the operating state of the vehicle transmission, in particular, take place exclusively by means of electric or electronic signaling (“shift-by-wire”) in an increasing number of motor vehicles.
However, the electric or electronic activation of such systems, which makes do without mechanical connection, leads to the circumstance that there will not be an unambiguous assignment any longer between the position of an actuating element and the state of the system that can be controlled by means of the actuating element, for example, a vehicle transmission. In other words, this means that the desired state of the system being controlled, for example, of the vehicle transmission, which is selected with the actuating element, does not agree with the actual shifting state of the system or transmission.
Such a divergence between the states of a technical system and the control elements thereof may have various causes.
For example, erroneous or non-functioning recognition of the position of the control element may be involved, with the consequence that the gear, preselected, for example, by the driver on the control element, was not recognized by the system and the corresponding control command was consequently not sent to the transmission. For example, erroneous or non-functioning transmission of the control command between the control element and the system controlled therewith is equally imaginable as well.
However, the situation in which technical systems, for example, vehicle transmissions, adapt their operating or shifting state to changed general conditions and change it automatically even without direct action of the driver, also occurs increasingly frequently in modern motor vehicles with the complex technical systems, which are increasingly interlinked with one another. For example, it is not uncommon that an electronic or shift-by-wire-controlled vehicle transmission automatically assumes the shift position P (parking brake) for safety reasons when the engine is stopped and after the ignition key is removed or as soon as the driver leaves the vehicle.
However, if the vehicle is equipped with a usual transmission actuating element, for example, with an automatic selector lever, the selector lever remains in the shift position selected manually by the driver before, for example, in “N,” even in case of the automatically engaged shift position “P.” The control lever thus falsely signals by its unchanged position in the “N” position that the transmission is in shift position “N,” whereas the transmission is actually in shift position “P” because of the automatic activation of the parking brake. While this may not directly lead to a safety risk in the example selected here, at least the problem still remains that the selector lever is in the “N” position when travel is next started, and difficulties or lack of clarity could therefore arise when engaging the desired gear.
The comparatively simple case in which the system being controlled is the windshield wiper unit of a vehicle is another example, which is used for illustration only. It is already known in this case as well that the windshield wiper turns on automatically because of corresponding sensor signals, for example, when heavy fog develops or when precipitation begins. However, this means that the operating state of the windshield wiper may no longer possibly agree with the switching state of the actuating element for the windshield wiper.
Thus, the actuating element falsely signals by its unchanged position in the off position that the windshield wiper is turned off, whereas it is actually in operation because of the automatic activation. Even if the actual operating state may also be easily recognizable in case of the windshield wiper, at least the problem still remains that the actuating element is already in the off position during the manual intervention in the automatic windshield wiper mechanism, which may possibly be desirable, i.e., to turn off the windshield wiper.
As can easily be seen, the cases from the area of the motor vehicle or the gear box control are only examples of generally applicable relationships in the man-machine interaction in case of electronically controlled technical systems, in which the actuating elements are not in connection with the system to be controlled via mechanical linkages or shafts any longer, but only via electric or electronic signals.
To solve the problem that there is not always an agreement between the position of the actuating element and the state of the system being controlled by means of the actuating element, it was proposed in the state of the art that such technical systems, especially automated vehicle transmissions, be actuated by means of an essentially rotationally symmetrical rotary switch, wherein the rotary switch is unlimitedly rotatable by itself.
The actuation position of the rotary switch which corresponds to the actual sate of the system to be controlled or to the actually engaged gear of the automatic transmission is set in this actuating device by means of the active adjustment of mobile end stops for the rotary switch. The adjustment of the end stops is performed in a variable manner as a function of the actual state of the system or the actually engaged gear. It is ensured in this manner that the relative position of the rotary switch between the end stops always agrees with the actual state of the system regardless of the switching position being assumed by the rotary switch and regardless of whether the state of the system was changed without an intervention on the part of the user.
However, this adjustment or motor-driven adaptation of the position of the end stops to the actual state of the system does require a certain effort. Moreover, the motor-driven adjustment of the end stops always takes a certain time until the end stops reach the intended position, and this adjustment time also varies, moreover, with the degree of deviation between the actual position and the desired position of the stops.
In addition, selective blocking of certain gear selection possibilities on the actuating element or rotary switch is desirable or necessary in certain cases, for example, in case of the control of an automatic transmission. For example, the driver must be prevented for safety reasons from engaging the reverse gear above a certain forward travel speed to prevent damage to the powertrain. However, besides the adjustment of the end stops for the rotary switch, a possibility of selective blocking or a possibility of controllably changing the distance between the two end stops of the rotary switch would be additionally necessary for this, but this would require a considerable additional design effort.